A triazolobenzodiazepine compound with antianxiety and sedative-hypnotic actions, that is efficacious in the treatment of panic disorders, with or without agoraphobia, and in generalized anxiety disorders. (From AMA Drug Evaluations Annual, 1994, p238)

This compound belongs to the benzodiazepines. These are organic compounds containing a benzene ring fused to either isomers of diazepine(unsaturated seven-member heterocycle with two nitrogen atoms replacing two carbon atoms).

Pharmacology

Indication

For the management of anxiety disorder or the short-term relief of symptoms of anxiety and for the treatment of panic disorder, with or without agoraphobia.

Pharmacodynamics

Alprazolam, a benzodiazepine, is used to treat panic disorder and anxiety disorder. Unlike chlordiazepoxide, clorazepate, and prazepam, alprazolam has a shorter half-life and metabolites with minimal activity. Like other triazolo benzodiazepines such as triazolam, alprazolam may have significant drug interactions involving the hepatic cytochrome P-450 3A4 isoenzyme. Clinically, all benzodiazepines cause a dose-related central nervous system depressant activity varying from mild impairment of task performance to hypnosis. Unlike other benzodiazepines, alprazolam may also have some antidepressant activity, although clinical evidence of this is lacking.

Mechanism of action

Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.

Absorption

Readily absorbed from the gastrointestinal tract. Bioavailability is 80-90%.

Volume of distribution

Not Available

Protein binding

80% (mainly to albumin)

Metabolism

Hepatic. Hydroxylated in the liver to α-hydroxyalprazolam, which is also active. This and other metabolites are later excreted in urine as glucuronides.